package com.atboluo.springcloud.lb;


import org.springframework.cloud.client.ServiceInstance;
import org.springframework.stereotype.Component;

import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;

@Component
public class MyLB implements LoadBalancer{
    // 原子类  ---> 其中的value 使用费 volatile 关键字修饰，实现多线程的同步，每次调用 + 1
    private AtomicInteger atomicInteger = new AtomicInteger(0);

    public final int getAndIncrement(){
        int current;
        int next;
        // 自旋锁
        do {
            current = this.atomicInteger.get();  // 0
            next = current >= 2147483647 ? 0 : current+1;
        }while(!this.atomicInteger.compareAndSet(current,next)); // CAS should
        System.out.println("************访问次数：next: " + next);
        return next;
    }

    @Override
    public ServiceInstance instances(List<ServiceInstance> serviceInstances) {
        int index =  getAndIncrement() % serviceInstances.size();

        return serviceInstances.get(index);
    }
}
